Collaborative projects in the environmental health sciences includes those projects in which the mass spectrometry work-group collaborates with other groups, both within and without the institute to solve problems of mutual interest. A major focus of these projects is the determination of xenobiotics in the environment, in living systems and the determination of their metabolic products. Their importance lies in the fact that the adverse interactions between compounds in the environment and their metabolite with living systems underlie our health concerns. These projects typically involve on-line separation and identification of complex mixtures and often involve use of all instrumental techniques available in the MS lab including thermospray LC/MS (TSP/LC/MS), FAB/MS and FAB/MS/MS (including the use of continuous flow techniques) and GC/MS. A typical project is the identification of the metabolites of H.C. Blue No. 1 and H.C. Blue No. 2. H.C. Blue No. 1 is a known carcinogen which differs only slightly from the non-carcinogenic H.C. Blue No. 2. The metabolic profiles in mice of these two compounds differ significantly. H.C. Blue 2 was observed to yield one major metabolic product. Using GC/MS, HR/MS and TSP/MS technique, this product has been identified as a side chain oxidation product. In contrast, the carcinogenic H.C. Blue 1 undergoes dealkylation to the free amine, from which a variety of metabolites arise. The free aromatic amines are known carcinogens. Therefore, the difference in carcinogenic behavior can be explained on the basis of their different metabolisms. Other projects, which are included in this heading, include analysis of airway epithelium prostaglandins, the determination of bradykinin in bovine milk, the identification of liver cell growth factor, and the identification of the products of free radicals with spin traps.